1. Field of the Invention
The present invention relates to a sheet aligning device disposed downstream of a feeder board for laterally aligning each of sheets of paper during the sheet is conveyed by the feeder board from a sheet feeder to a printing unit and a method of controlling the same, and more specifically a sheet aligning device for laterally aligning each of sheets of paper, which has plural aligning plates capable of being reciprocatingly moved in a direction orthogonal to the sheet conveying direction and a method of controlling the same.
2. Related Art
A feeder board that conveys sheets of paper (hereinafter simply referred to sheets) from a sheet feeder to a printing unit is provided with a sheet aligning device (also called as a pulling device) for lateral alignment of each sheet. This aligning device has an aligning plate (also called as a pulling plate) with a sheet abutting surface parallel to the sheet conveying direction, which is reciprocatingly movable in a direction orthogonal to the sheet conveying direction, so that the aligning plate is preset at a given position to allow each sheet conveyed to have its lateral side abutting against the sheet abutting surface, thereby limiting the lateral displacement or offset of each sheet and hence laterally aligning each sheet.
As described in Japanese Patent Application Laid-open No. 2000-280453, it is known that an additional aligning plate is disposed opposite to the aforesaid aligning plate on the opposite lateral sides of the feeder board so that the lateral displacement or offset of each sheet is limited by at least one of the oppositely disposed aligning plates, according to the size of the sheets or the printing mode.
According to the above arrangement having the aligning plates disposed opposite to each other on the opposite lateral sides of the feeder board, one of the aligning plates is used for alignment, while the residual one is retracted as far as possible towards a corresponding lateral side of the feeder board.
According to needs and circumstances, each aligning plate is sometimes provided with a sheet pulling device made up of such as a pressing roller for pulling each sheet towards the sheet abutting surface, or is incorporated with a guide mechanism in the form of, for example, a bellows mechanism whose end is mounted to a laterally inward side of the aligning plate, which side is located close to the axis or centerline of the sheet to be conveyed so as to prevent intrusion of foreign matters such as a sheet into a moving path of the aligning plate. Meanwhile, a limited space of a printing press or the feeder board may poses a possibility that a lateral side of a sheet, if the sheet has an excessive size or the like, passes on the aligning plate out of use for alignment, even when the aligning plate is retracted to a farthermost position close to the corresponding lateral side of the feeder board. When the sheet side passes over the sheet pulling member of the aligning plate or the mounting portion of the guide mechanism, the sheet may be blocked or interrupted at these positions, causing the sheet is obliquely displaced from the right place. This may lead to a problem of poor alignment of the sheet in the lateral direction and hence errors in registration for printing.
It is an object of the present invention to provide a sheet aligning device that includes aligning plates disposed on the opposite lateral sides of a feeder board so as to allow any one of them to be operated for alignment of sheets and that is capable of preventing errors in registration for printing, and a method of controlling the same.